To date, the main effort of GaN electronics has been on depletion mode (D-mode) devices, while enhancement mode (E-mode) devices have been less extensively studied. However, E-mode devices are attractive for low-power digital applications, normally-off power switches, and high-efficiency RF applications. The integration of E- and D-mode devices on the same die would enhance the functionality of GaN components greatly. Several approaches to making E-mode devices on the same wafer as D-mode devices have been investigated, including Barrier layer (AlxGa1-xN) gate recesses, fluorine treatment, and buffer backbarriers [3-5]. Barrier layer (AlxGa1-xN) gate recesses and fluorine treatment have the flexibility of masking during processing, allowing integration of E- and D-mode devices on the same wafer [3, 6]. However, the dry plasma etching processes which are typically used for III-nitride processing can create damage in the material under the gate, and fluorine treatments suffer from poor controllability and reliability concerns. Selective buffer backbarriers (between the Substrate and the Channel layer) avoid problems associated with recess etching and fluorine treatment, but integration of E- and D-mode devices on the same wafer has not been shown.